1. Field of the Invention
The present invention relates to a semiconductor apparatus and a method for producing it and, more particularly, to a semiconductor apparatus having a thin film transistor (TFT) matrix panel, which is suitably applicable, for example, to formation of a liquid crystal display apparatus or a photoelectric conversion apparatus, and a method for producing it.
2. Related Background Art
It has been a widespread practice heretofore to construct a display unit of a display device such as a liquid crystal panel or the like or a reading unit of a photoelectric conversion device such as an area sensor of a lot of display pixels or reading pixels arrayed in an X-Y matrix and to carry out signal input to each pixel or signal reading from each pixel by an X-Y matrix driving method via TFT provided for each pixel. The display pixels of the display device can be constituted using a liquid-crystal display element in which the liquid crystal is interposed between a pair of electrodes at least one of which is transparent, and the reading pixels of the photoelectric conversion device can be constituted using a photoelectric conversion element in which a semiconductor photoelectric conversion layer is interposed between a pair of electrodes.
Such TFT panels having the matrix array of TFT-provided pixels are increasing their size quickly in recent years. This tendency is due to development in the production technology of liquid-crystal display apparatus using the TFT panel and utilization of the area sensor having the photoelectric conversion element in various fields (for example, application to X-ray image pickup apparatus). Together with this size increasing tendency, micronization is proceeding of array pitches of the pixel pattern. With these panel increasing tendency and pixel micronization tendency, decrease is encountered in the yield in TFT panel production steps. Conceivable reasons are as follows:
(1) a wiring distance per panel has been increasing with progress in the size increasing tendency of the panel, and a discontinuity probability becomes higher therewith; PA1 (2) the area of TFTs and wiring cross portions per panel has been increasing with progress in the micronization tendency of the pixel pattern of panel, and a short probability thus becomes higher between upper and lower metal wires; PA1 (3) electrostatic damage (ESD); specifically, the area capable of contacting the outside has been increasing with the size increasing tendency of panel, so as to increase the quantity of static electricity generated, which results in increasing the probability of occurrence of failure due to ESD. PA1 wherein an end of said bias line on an opposite side to a connection side to a common electrode driver for applying a bias is electrically connected by a bias redundant wire to an end of another bias line on the opposite side to the connection side to the common electrode driver for applying the bias.
Increase of yield can be secured by solving these technological issues. Among these reasons, however, (1) can be solved by increasing the wiring width, whereas (2) can be solved by decreasing the area of cross portions between the upper and lower metal wires, i.e., by decreasing the wiring width of the cross portions to the contrary. The increase in the thickness of wiring results in increasing the wire-to-wire capacitance established between the upper and lower metal wires and in turn lowering the sensitivity of transferred signals. It is also conceivable to accomplish the increase of yield by forming a redundant circuit, but the problem of the decrease of sensitivity can also arise in certain cases where an aperture rate of pixel capacitor portions is decreased because of the redundant circuit. As described above, the design of wiring width is now extremely difficult.
FIG. 1 shows an example of equivalent circuitry of a TFT matrix panel.
In FIG. 1, reference numeral 1 designates a TFT matrix panel in which TFTs (thin film transistors) 3 are arrayed in a matrix, 4 capacitors or photoelectric conversion elements (which are indicated as capacitances of photodiodes or the like, capacitances of MIS (Metal Insulator Semiconductor) type photosensors, or capacitances of charge storage capacitors combined with photoconduction type photosensors herein), 5 transfer lines (Sig lines) for transferring signals, 6 bias lines (Vs lines), 7 gate lines (Vg lines), 11 a signal processing circuit having an amplifier, 12 a common electrode driver, 13 a gate driver, and R1, R0 respective wire resistances, A a discontinuity portion, and B a short portion.
In FIG. 1, C.sub.11, C.sub.12, . . . , C.sub.21, C.sub.22, . . . , C.sub.5n each denote the capacitors or photoelectric conversion elements 4, t.sub.11, t.sub.12, . . . , t.sub.21, t.sub.22, . . . , t.sub.5n the TFTs 3, V.sub.s1, V.sub.s2, . . . , V.sub.s5 the bias lines 6, and Dr.1, Dr.2, . . . , Dr.n gate drivers corresponding to the respective gate lines.
In the semiconductor apparatus illustrated in FIG. 1, the plurality of TFTs (t11 to tmn) 3 arrayed in the matrix are driven by a bias voltage supplied from Dr.1 to Dr.n of the gate driver 13 to the plurality of gate lines 7 (for example, Cr (chromium) wires), and electric signals obtained by the photoelectric conversion elements coupled with the respective TFTs forming the respective pixels are transferred from the first electrode of the photoelectric conversion elements c11 to cmn through the plurality of transfer lines 5 (for example, Al (aluminum) wires) to the signal processing circuit 11, thereby effecting signal reading from each matrix element or pixel.
The second electrodes of the photoelectric conversion elements (c11 to cmn) are connected to the plurality of bias lines 6 (for example, Al wires) connected to the common electrode driver 12.
FIG. 2 is an example of a pattern diagram at a corner portion on the opposite side to the bias application side to the bias lines 6 by the common electrode driver 12 in the TFT panel of FIG. 1.
In the production of this TFT panel, when a discontinuity appears in the bias line Vs2, as indicated by symbol A in FIG. 1, the capacitors or photoelectric conversion elements (c22 to c2n) are separated from the common electrode driver 12, and the pixel to which this capacitor or photoelectric conversion element belongs, and the pixels below this defect become defective pixels; a line-shaped defect appears in many cases. When a short circuit occurs between a bias line and a gate line because of attachment of foreign matter or the like, as indicated by symbol B in FIG. 1, defects appear along the bias line and the gate line, because the desired voltage is not applied to the both short-circuited lines. Such occurrence of defects was the cause of decreasing the yield of production.